1. Field of the Invention
The present invention is directed to a medical X-ray diagnostics installation and a method for operating same, the installation being of the type having an X-ray source, with a filter optionally introducible into the beam path, and a detector that receives the X-radiation having individual picture elements and which supplies image signals pixel-by-pixel dependent on the received radiation, and a computer for image generation and output.
2. Description of the Prior Art
The exposure of an X-ray image usually ensues by first making a fluoroscopic exposure of the examination subject in order to obtain information in view of, among other things, the illumination distribution of the X-ray exposure. If it turns out that regions of excessively great illumination exist within the exposure, which can be the case due to subject locations of different density and thus different absorbency, then these can be largely eliminated by introducing a corresponding filter, for example a wedge filter or a graduated filter, into the beam path. The radiation dose applied to the subject in this region, and thus the dose ultimately reaching the detector as well thus being reduced, i.e. filtered. The positioning of the filter, for example semi-transparent diaphragm lamellae, is thereby manually carried out by the operator, who inserts the filter into the beam path in conformity with the knowledge about the over-irradiated regions. A further fluoroscopic exposure is required in order to know the correct position of the filter and its filtering effect and in order to decide whether the positioning is adequate, i.e. another radiation image must be registered. This, however, is extremely disadvantageous, particularly since the patient must be exposed to a radiation dose again. Further, the implementation of the second fluoroscopic exposure is disadvantageous for the overall examination sequence itself, particularly in view of time.
PCT Application 84/04878 A1 discloses a method as well as an apparatus for the production of filters that are subsequently introduced into the beam path. The production ensues such that a filter is arranged in the beam path in the framework of a first fluoroscopic exposure. Dependent on the transmission signals identified with a pick-up unit, a filter material is then deposited on the filter with an appropriate device. After the production of this filter, it is subsequently placed into the beam path, after which the actual second exposure ensues.